Method of making seamless platinum ruthenium alloy cannulae



Patented Nov. 16, 1948 UNITED STATES PAT ENT OFFICE of Pennsylvania NoDrawing. Original application February 27, 1941, Serial No. 380,960.Divided and this a plication July 1-4, 1945, Serial No. 605,180

1 Claim. 1

This invention relates to a method for the production of seamlessso-o'alled platinum or platinum alloy cannulae for hypodermic needles.

In the past it has been customary to make the cannula'e for so-alledplatinum hypodermic needles from platinum-iridium and platinumgoldalloys. The alloys most commonly used were 70% platinum with 30% iridiumand 75% platinum with 25% gold.

The procedure generally followed in the manufacture of such plaitinumiridium and platinumgold cannulae consists in alloying the metals bymelting and then casting an ingot thereof. In the case ofplatinum-iridium the ingot is hot forged and cold rolled to a thicknessof about .015 inch and then cold rolled with intermediate annealingstages to the desired thickness, ge'ner ally about .003 inch. From theresulting rolled sheet, strips are cut to a predetermined size and eachstrip is drawn into tubular form through a series of dies until theedges of the strip are brought closel together, i. e. exactly but't'edtogether but not overlapping. Then apiece of small diameter gold Wi-r'e,generaliy .005 inch, is inserted within the tube and held in place overthe butted edges of the open seam tube. The tube and wire are thanpassed through a name of such a temperature as to almost instantly ineltthe gold wire which enters into the seam and also deposits on the insideof the tube over the seam. The resulting tube is then tested for leaksand, if satisfactory, is drawn through a succession of dies to thedesired finished size.

The manufacture of 'platinurn gold tubing is similar to the "generalprocedure described above for the manufacture of platinumqr'idium tubingexcept that the platinum-gold alloy is not not worked, although it issubjected to annealing 'at predetermined stages. I

During the gold soldering operati'dn described above, it is necessary inthe case "of platinumiridium to heat the tube Within a very narrowtemperature range and within a Very short period of time, i. e. aboutone or two seconds. If the temperature is too high or if the tube isheated for too long a time the gold solder combines with theplatinum-iridium and forms a very brittle alloy. If, on the other hand,the temperature is not high enough only a, partial or incomplete bond isachieved and in some instances there is no bond at all. If a poorbond isformed the tube may open either during the final manufacturing operationor in use.

The same limitations apply in the soldering 2 of 'platiniim 'gold tubingwith gold but to a lesser degree.

It is to be observed that in the above described procedure at no timeafter the tube has been soldered is a mandrel or arbor used insideeither the platinum-iridium or the platinum-gold tube for the purpose ofsupporting the tube wall during drafting or for the purpose of smoothingout irregularities "on the inside of the tube. It has been found to beimpractical to use a mandrel or arbor for these purposes within thesoldered tubes because the brittle nature of the seam or area adjacentto the seam precludes following the "common practice 'of subsequentlyexpanding the tube by mechanical means to permit the mandrel or arbor tobe withdrawn.

Since the practice of gold soldering does not produce uniformly smoothinternal surfaces, cannulae made by this practice frequently containinternal irregularities which permit the accumulation or objectionableforeign substances.

-At times excessivegold solder wiil remain inside the tube in the formof a film and will flow and form small beads on the inside of the tubeif the ne'edle is heated excessively during flame sterilization. "Suchbeads may partly or even Wholly/close the 'cannuhe and thus retard orprevent the now of the liquid to be injected.

When the gold-soldered tubing is made into needles the sol'd'ered seammay open because of imperfect bonding or because of embrittlement of thealloy adjacent the seam.

Further, when the soldered cann'ulae are being pointed care must betaken that the seam comes at the "top "or heel "of the point.

All o'f these disadvantages increase the cost and lower the Value of aninherently expensive article.

An object bf the present invention is to produce tubing, cannulae andneedles which shall have al' l of the advantages of the go1d-solderedplatinum-iridium and platinum-gold tubing, cannulae and needlesheretofore produced and which shall be "free of many of theirdisadvantages. This object is attained in accordance with "the presentinvention by so manipulating the alloy as to produce seamless tubing,cannulae and needles therefrom.

some of the desirable characteristics of cannul'a'e and hypodermicneedles are the followmg:

(1) They must be stiff but not brittle.

(2) 'Th'eymust be free of structural imperfections such as cracks,roughness, etc.

(3) Thevmustbecapame of flame'sterilization without damage such as lossof stiffness or development of brittleness.

(4) They must not split or clog especially as a result of flamesterilization.

(5) They must not tarnish or corrode.

(6) They must have a uniform grain structure and hardness.

(7) The manufacturing process should be relatively simple andinexpensive and the product uniform and reliable.

(8) The tubing should be capable of being cut and of being mounted inthe needle hub without splitting or collapsing.

(9) They should not be excessively costly.

We have found that alloys of platinum and ruthenium of suitable grainstructure, hardness and stiffness may be fabricated into seamless tubessuitable for use as the cannulae for hypodermic needles and that suchneedles have in general all of the advantages and none of thedisadvantages of the gold-soldered platinumiridium and platinum-goldneedles discussed above. We started with an alloy of about 89% platinumand about 11% ruthenium because this alloy in the cold-worked state hasa hardness comparable with that of the alloy'of 70% platinum and 30%iridium heretofore used for needles but we have found that thecomposition of the alloy may vary within the range from 820% ofruthenium and from 92 to 80% of platinum. The substitution of part ofeither or both the platinum and ruthenium by palladium, iridium andrhodium or combinations thereof in amounts which do not alter theessential workable characteristics of the alloy for use as cannulae forhypodermic needles and the presence of other metals in inconsequentialamounts is not excluded. We have found, for instance, that alloyscontaining 15% and more by weight of ruthenium, the remainder beingplatinum. are workable into cannulae, possess greater hardness than the11% alloy and are otherwise suitable for use in hypodermic needles. Thehardness is referred to particularly because sufficient hardness andstiffness without brittleness are outstanding characteristics ofhypodermic needles made of such platinum-ruthenium alloys. Incidentally,the

platinum-ruthenium alloys'have'a lower specific gravity thanplatinumdridium and platinumgold alloys and consequently yield a greaterquantity of cannulae per unit of weight.

Seamless tubing of the platinum-ruthenium alloys may be made by any ofthe following three methods:

(1) By making a relatively large, open-seamed tube, fusing together theabutting edges without the use of a welding or soldering material andproceeding with the tube drawing practice within the limits of annealingand mechanical working described below.

(2) By deep drawing a cup from a sheet of the alloy and proceeding withthe tube drawing practice described below.

(3) By casting a round ingot, hot working and then drilling itlengthwise to form a tube, and then proceeding with the tube drawingpractice described below.

All three of the above methods of forming the initial tube are known inother relations but are, so far as we are aware, novel inthe productionof satisfactory platinum alloy cannulae for hypodermic needles.

The initial steps of methods 2 and 3 are applied to theplatinum-ruthenium alloys in exactly the same Way as to other metals .inthe production of tubing and therefore need not be described in detail.The tube drawing practice of methods 2 and 3 is the same as in method 1and will be described in the following detailed description of method 1.

The platinum-ruthenium alloy, e. g. an alloy of about 89% platinum and11% ruthenium is produced by melting the elements together and castingan ingot. The ingot is hot forged and hot rolled to a sheet of about.050 inch thickness. The sheet is then alternately cold rolled and anhealed until a thickness of about .020 inch is reached."- 'At thisthickness the sheet is cut into strips of suitable'size, say 18 incheslong by .875 inch wide, and bent to a U-shape cross section in asuccession of open dies using a round arbor to maintain the innercontour. The U-shape piece is removed from the last of the succession ofopen dies and the edges are brought down snugly on the arbor byhammering and then both tube and arbor are passed through a swagingmachine in order to bring the edges tightly to gether. The arbor is thenremoved and after proper cleaning the edges are fused together. The sizeof the tube will be about .187 inch internal diameter and .227 inchexternal diameter. It will be understood that in the foregoing thethickness of the sheet and the size of the tube are given merely asexamples and not as limitations. Both the thickness of the sheet and thediameter of the tube may be varied.

Care must be taken in fusing together the edges of the tube. The fusedsection has the nature of a cast structure and for this reason the tubeis next thoroughly annealed at a temperature not less than 2000 F. inorder to produce a more homogeneous structure by reduction of thedendrites in the cast metal.

It is observed that at this point the diameter of the seamlessplatinum-ruthenium tube is much larger and the walls are much thickerthan the platinum-iridium and platinum-gold tubes heretofore produced bygold-soldering as described above. This has a distinct advantage in thatit permits a more extensive working of the metal of the tube in reducingits diameter and wall thickness to that required for the cannulae, thiswork serving to remove all traces of the cast structureof the seamproduced by fusing together the edges of the sheet in forming the tubeand thereby to give a truly seamless tube.

The formed and annealed tube is now ready for reduction to the desiredfinished size. For example, if a hypodermic needle'cannula of .025 inchoutside diameter and .005 inch wall thickness is to be made, thefollowing procedure is used. The formed and annealed tube is swedgedover a mandrel to create a uniform wall thiclz ness and smooth externaland internal surfaces. It is then alternatel annealed and swedged untilthe outside diameter has been reduced to .202 inch and the insidediameter to about .160 inch, the wall thickness being maintained atabout .020 inch. The tube is then annealed and after cooling put on a.142 inch diameter mandrel and the tube and mandrel drawn through a dieof .182 inch diameter, the tube wall thickness thus being maintained at.020 inch. The tube is then slightly expanded by passage through aswedging machine and the mandrel removed. The tube is then annealed, the.142 inch mandrel reinserted and the' This reduces the tube wallthickness tions similar to that last described but using progressivelysmaller mandrels and dies, is brought to an external diameter of .098inch and a wall thickness of .004 inch. At this point the last mandrelis removed and the tube is sunk, without further annealing or use ofmandrels, through a succession of 11 dies to reduce the outside diameterof the tube to say .025 inch, the wall thickness thereby being increasedto about .005 inch. The tube is then cut into suitable lengths, pointedand mounted as usual in the manufacture of hypodermic needles.

The above described drawing practice is, so far as we are aware, new asapplied for the production of seamless tubing suitable for use ascannulae for hypodermic needles from platinum group metal alloys ofsufficient hardness for this use. The method, i. e. the application ofthe drawing practice to such alloys, is the result of a careful study ofthe characteristics of platinumruthenium alloys containing 8 to 20% ofruthenium and of the relation of physically working the alloys withincertain limits of both temperature and mechanical practice.

The tubing, cannulae and needles, as compared with platinum alloytubing, cannulae and needles heretofore available, constitute a new andvaluable addition to the field of hypodermic needles as a whole. Theyare characterized particularly by their freedom from any seam and byfreedom A from mechanical and metallurgical imperfections associatedwith a seam. The tubing or cannulae may serve for any of the variety offorms or types of hypodermic needles such as the Luer type, the spinalpuncture type, the type commonly used in dental work, etc. The mandrelpractice followed in the manufacture of the tubes has the highlyimportant effect of producing tubes the insides of which are perfectlysmooth, and it is significant that this inside smoothness persiststhrough the of being sterilized by heating to redness by means of anopen flame repeatedly without loss of stiffness, are free of mechanicaldefects such as internal roughness, weak seams and tendency to split,are free of solder which might clog the tube upon flame sterilization,and are of uniform grain structure and free of segregation.

This application is a division of our application Serial No. 380,960,filed February 2'7, 1941, now abandoned.

We claim:

Method of making a seamless cannula for a hypodermic needle whichcomprises forming a tube of homogeneous platinum metal alloy,alternately annealing the tube and swedging the tube over a mandrel withreduction of the tube diameter while maintaining its wall thickness,alternately annealing the tube and drawing the tube on a mandrel withreduction of the tube diameter andwall thickness, and finally sinkingthe tube through a succession of dies to reduce its outside diameter toa size suitable for use as a hypodermic needle cannula, the platinummetal alloy consisting essentially of platinum alloyed with from about8% to about 20% by weight of ruthenium and the seamless tube initiallybeing formed by hot forging and hot rolling an ingot of the alloy to athickness of about .050 inch, thereafter alternately annealing and coldrolling the sheet to a thickness of about .020 inch, forming the sheetinto a tube, fusing together the edges of the sheet and annealing theresulting tube at a temperature not less than 2000 F.

GEORGE M. HICKEY. WILLIAM W. MATLACK.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,295,430 Carlson Feb. 25, 19192,208,606 Smith July 23, 1940 2,300,353 Eberhardt Oct. 27, 19422,368,381 Schmitt Jan. 30, 1945

